Textile machine with recirculating air heating effected by gas-heated head exchangers

ABSTRACT

A textile machine having circulating air heating by means of gas-heated heat exchangers, having flame or meander tubes arranged parallel to one another in a suction space, crosswise to the air stream of the latter, and burners switched ahead of them, is described. In order to be able to work with two burners in the case of high required heat output, and nevertheless to heat the air stream drawn in by the heat exchanger equally, in the case of indirect circulating air heating, everywhere in the stream cross-section, two burners, each having a subsequent tube heat exchanger, are each assigned to one half of the suction space, whereby the heating tubes of the two heat exchangers reach over the entire suction space width, in the main part of the suction space, crosswise to its air stream, but extend only over the suction space half assigned to the burner, in each instance, at least in a segment of the circulating air stream path in the suction space.

The invention relates to a textile machine having circulating airheating by means of gas-heated heat exchangers, having flame tubesarranged parallel to one another in a suction space, crosswise to theair space of the latter, particularly meander tubes, and burnersswitched ahead of them. Preferably, flow through adjacent flame tubes issupposed to take place in anti-parallel manner. The textile machinepreferably has a device for indirect heating of the treatment gas, inthe housing of which a cross-counter-current recuperator configured bymeans of the invention is arranged.

The circulating air heating is provided, in the case of convectiondrying machines and/or fixing machines, for the thermal treatment of atextile web of material. Examples of such machines are stentering framesand hot flues (see these key words in Koch, Satlow, GrossesTextil-Lexikon [Big Textile Encyclopedia], Deutsche Verlags-AnstaltStuttgart, 1996). Devices for continuous shrinkage treatment of textilewebs of material and machines for drying filament warps or coatedcarpets, according to DE-PS 27 54 438, belong to the area of applicationof the invention.

DE 100 47 834 A1 describes a textile machine having a device forindirect heating of the treatment gas, which contains across-counter-current recuperator arranged in a housing. The recuperatoris structured in such a manner that the sum of the temperature valuesthat are measured on a straight line in the circulating air streamdirection, in each instance, at the flame tube parts which the linehits, is the same everywhere in the cross-section of the heat exchanger(that lies perpendicular to the circulating air stream). The energytransferred in the heat exchanger is applied by a burner.

In the case of conventional textile machines of the type indicatedabove, combustion gases intended for heating are directly mixed with thecirculating air; one then speaks of direct heating. The combustiongases, which are generally produced by burning gas or oil, then comeinto direct contact with the textile web of material. If this issupposed to be avoided, the aforementioned indirect heating can be used.

In the case of indirect heating, heat exchangers having oil circulationor steam heating are generally used. These heat exchangers guaranteethat the circulating air stream to be heated, the volume andcross-section of which (determined by the consumption in the jet systemto be supplied) are relatively large, is given the same temperatureeverywhere in the stream cross-section. The latter is a prerequisite forthe fact that the treatment agent stream formed by the circulating airstream, e.g. in jet boxes, has the same temperature everywhere on thetreated surface of the textile web of material. This advantage isachieved at great expense, however, if heating systems for operation ofheat exchangers heated by means of circulating oil or steam are absentat the user's facilities, in other words significant additionalinvestments are required even if application cases with indirect heatingoccur only now and then.

If a very great output is demanded in the textile machine in question,which is to be heated, e.g. in a hot flue, it is difficult for therequired amount of energy to be applied by only a single large burner.Instead, it has proven to be more advantageous, in practice, to use twosmaller burners. However, the general requirement of heating the textileweb of material that is to be treated evenly everywhere on its surface,particularly on every line crosswise to the transport direction, mustalso be fulfilled when using two burners.

If two smaller burners are provided instead of one large burner, in thecase of the directly heated machines, a uniform distribution of thecirculating air temperature on the surface of the web of materialcrosswise to the circulating air stream can be achieved if each of thetwo burners has its own temperature regulation circuit. In thisconnection, the temperature sensor for the burner located on one side(e.g. the right) is arranged in that fan housing that is assigned to thesame side, in other words the right side of the web of material, whilethe temperature sensor for the burner on the other (left) side isarranged in the fan housing that is located there (i.e. on the left).The two partial streams are mixed with one another in various suctionand pressure spaces, using complicated circulating air mixers, so that auniform temperature distribution is achieved over the width of the webof material, in every case, when it impacts the material. The separatetemperature regulation is necessary because it is hardly possible tocontrol both burners in absolutely equal manner from a single regulator.This is attributable to the tolerance and the hysteresis of theregulating valves for the energy supply, e.g. the gas supply.

According to a recognition on which the invention is based, it appearsnecessary, in the case of indirect heating of the treatment gas, toprovide a separate heat exchanger for each of the (smaller) burners.Nevertheless, it is desirable, in the sense of the aforementioned DE 10047 834 A1, to eliminate the complicated circulating air mixers in orderto achieve an air stream that is equally tempered everywhere over itscross-section. Instead, it should be possible to arrange and configurethe flame tubes in such a manner that the sum of the temperature valuesthat are measured on each line parallel to the circulating air stream,from flame tube to flame tube, is the same everywhere in thecross-section (that lies perpendicular to the circulating air stream) ofthe total heat exchanger channel assigned to the burners in common.

The invention is based on the task of achieving these goals for twoburners for indirect heating of the treatment gas with across-counter-current recuperator, whereby each of the two burners issupposed to contain its own temperature regulation circuit with its owntemperature sensor and its own regulating valve (for the energy supply).

For the textile machine described initially, the solution according tothe invention consists in the fact that two burners, each having asubsequent tube heat exchanger, are each assigned to one half (the rightand the left half, respectively) of the suction space, and that theflame tubes of the two heat exchangers reach over the entire suctionspace width, in the main part of the suction space, crosswise to its airstream, but extend only over the suction space half assigned to theburner, in each instance, at least in a segment of the circulating airstream path in the suction space. In other words: In order to be able towork with two burners in the case of high required heat output, andnevertheless to heat the air stream drawn in by the heat exchangerequally, in the case of indirect circulating air heating, everywhere inthe stream cross-section, the burners, each having a subsequent tubeheat exchanger, are each assigned to one part of the suction space,whereby the heating tubes of the two heat exchangers reach over theentire suction space width in the main part of the suction space,crosswise to its air stream, but extend only over the suction space partassigned to the burner, in each instance, in at least one part of theair stream path in the suction space. Some improvements and additionalembodiments of the invention are indicated in the dependent claims.

According to the invention, the tubes of the two heat exchanger partsare arranged in such a manner that in the main part of the heatexchanger, one tube layer of the first heat exchanger alternates withone of the second heat exchanger, in each instance. In this connection,the combustion gases flow within the flame tubes, while the circulatingair to be transported to the textile web of material and heated ispassed around the tubes. The heat exchange takes place at the surface ofthe tubes, the heat of the combustion air is passed to the circulatingair there.

According to the invention, the flame tubes of the two heat exchangersare passed over the entire width of the suction space in their mainpart, preferably in meander shape. In at least one segment, preferablythe first and/or the last segment, on the circulating air path throughthe suction space, the flame tubes in which the combustion gases of theone burner, e.g. the right burner flow, are passed only through theright half of the suction space, while the flame tubes of the otherburner, in other words the left burner, lie only in the left half of thesuction space. Fundamentally, what is involved is part of the suctionspace. Subsequent to the heat exchanger, the combustion gases are passedinto a collector and drawn out of the machine from there.

Because the flame tubes are located only in the half of the suctionspace that belongs to one of the burners, on a segment of thecirculating air path through the heat exchanger, separate temperatureregulation of the circulating air on this half, and therefore regulationof the related burner, is made possible.

The partial division of the heat exchanger, according to the invention,can preferably be provided at the beginning and/or at the end of thecirculating air path in the suction space. The divided segment of theheat exchanger can, however, fundamentally be arranged at any locationof the heat exchanger, e.g. also somewhere in the middle of thecirculating air path.

By means of the invention, a heat exchanger supplied by two burners, forindirect circulating air heating, is created, which allows precise,separate regulation of the two burners, but can be produced withsignificantly less effort than if each burner had a separate heatexchanger assigned to it, in total. The heat exchanger, which is notdivided, for the most part, according to the invention, can be producedmore inexpensively, for example, than two separate heat exchangers,since only half of the welding work has to be performed in the undividedpart of the heat exchanger (as compared with complete division).

For precise regulation of the two burners, it has proven to besufficient if less than ten percent (in general, two meander loops, orpreferably, a single meander loop is sufficient) is divided in the senseof the invention. A cross-counter-current recuperator according to theinvention, for indirect heating of a treatment gas, possessed four flametube loops that extend over the entire width, crosswise to thecirculating air stream, which are supplied by each of the burners, and,for each burner in addition, one flame tube loop that extends over halfof the circulating air cross-section.

Details of the invention will be explained using a schematic exemplaryembodiment.

The attached drawing shows a heat exchanger channel 2 cut parallel tothe circulating air stream 1. The heat exchanger channel 2 possesses aninput 3 and an output 4 and longitudinal walls 5 and 6 that lie oppositeone another. The channel 2 comprises a right half 7 and a left half 8.The halves 7 and 8 each have a burner 9 and 10 assigned to them. Twoflame tubes 11 and 13, respectively, are supplied by each burner. Theflame tubes are preferably guided through the heat exchanger channel 2in meanders 15, 16 that run anti-parallel to one another. The meandertubes 11 and 13 in the drawing run crosswise to the circulating airstream 1 and meander in the direction of the circulating air stream 1.

In a main part 17 of the meander 15, 16, the flame tubes 11 as well asthe flame tubes 13 are passed back and forth crosswise over the entireheat exchanger channel 2, in other words from longitudinal wall 5 tolongitudinal wall 6. In a segment 18 or 19, respectively, which islocated at the end of the channel 2 in the circulating air streamdirection, in the exemplary embodiment, in contrast, the flame tubes 11meander only in the right half 7 and the flame tubes 13 meander only inthe left half 8 of the heat exchanger channel 2. These segments 18, 19each have a temperature sensor 20, 21 assigned to them, which controlsthe related burner 9 or 10, respectively, by way of a regulator 22 or23, respectively (along the line of effect as shown in the drawing), insuch a manner that the circulating air stream 1 that exits at the output4 has the same temperature everywhere, over the entire circulating airstream cross-section, from the longitudinal wall 5 to the longitudinalwall 6 (and crosswise to this direction). After the heat exchanger, thecombustion gases can be passed into a collector by way of heatingoutlets 24, 25, and from there drawn out of the machine.

The following example will show how the temperature regulation accordingto the invention can work: It is assumed that the combustion gases ofthe right burner 9 are 20° Celsius hotter than the combustion gases ofthe left burner 10 (800° Celsius as compared with 780° Celsius). For thesake of simplicity, it is furthermore assumed that this is also thesurface temperature of the tubes 11 and 13, respectively, at the inlet.The combustion gases cool down as a result of the heat transfer to thecirculating air, in the manner indicated by the temperature informationshown in the drawing. If the surface temperatures of three stream pathsof the circulating air, in each instance, are now followed in the rightand the left half 7, 8, and if the surface temperatures of thecirculating air stream paths, in each instance, are added, it is foundthat in the right half 7, in other words where the combustion gasesflowed into the tube bundles at a slightly higher temperature, highertemperature sums are also obtained than in the left half 8 (sum of thesurface temperatures in the right stream paths 5,700/5,680/5,660°Celsius; sum of the surface temperatures in the left stream phases5,600/5,620/5,640° Celsius). The sensor 20 of the right burner 9 givesthe latter a signal to throttle the supply of energy until the actualvalue of the left burner 10 has been reached.

REFERENCE SYMBOL LIST

 1 = circulating air stream  2 = heat exchanger channel  3 = input  4 =output  5 = left longitudinal wall  6 = right longitudinal wall  7 =right half  8 = left half  9 = right burner 10 = left burner 11 = flametubes (28) 13 = flame tubes (29) 15 = meander (28) 16 = meander (29) 17= main part 18 = right divided tube segment 19 = left divided tubesegment 20 = right temperature sensor 21 = left temperature sensor 22 =right regulator 23 = left regulator 24 = right heating gas outlet 25 =left heating gas outlet

1. Textile machine having circulating air heating by means of gas-heatedheat exchangers, having flame tubes (11 and 13) arranged parallel to oneanother in a suction space, crosswise to the air stream (1) of thelatter, and burners (9, 10) switched ahead of them, wherein two burners(9, 10), each having a subsequent tube heat exchanger, are each assignedto one half (7, 8) (the right and the left half, respectively) of thesuction space, and that the flame tubes (11 and 13) of the two heatexchangers reach over the entire suction space width, in the main part(17) of the suction space, crosswise to its air stream (1), but extendonly over the suction space half (7, 8) assigned to the burner (9, 10),in each instance, at least in a segment (18, 19) of the circulating airstream path (1) in the suction space.
 2. Textile machine according toclaim 1, wherein the divided segment (18, 19) of the flame tubes (11 and13) is located in the input region or in the output region of the airstream path (1).
 3. Textile machine according to claim 1, wherein thedivided segments (18, 19) of the flame tubes each have at least onetemperature sensor (20, 21) assigned to them, and that the temperaturesensors are switched with the related burner (9, 10) by way of aregulator (22, 23), in each instance.